KR20060108792A - Electrode, method for preparing the same, binder composition and lithium battery containing the materials - Google Patents

Abstract

The present invention discloses an electrode produced comprising a binder and an active material comprising a dispersed polyurethane polymer compound.

The electrode according to the present invention improves the adhesive strength by using a polyurethane polymer compound dispersed in water, and by curing the polymer compound having excellent dispersion characteristics by a crosslinking reaction, it is possible to control the elasticity and adhesive force while improving the elasticity and employing it. It is possible that one battery has improved restoring force and charge / discharge characteristics.

Description

Electrode, method for preparing the same, binder composition and lithium battery employing the same {Electrode, method for preparing the same, binder composition and lithium battery containing the materials}

1 is a stress-strain curve of the water-dispersed polyurethane polymer film according to Preparation Example 1 and Preparation Examples 7 to 11.

2 is a stress-strain curve of the water dispersion polyurethane polymer film according to Preparation Example 6 and Preparation Examples 12 to 16.

FIG. 3 is a graph showing shear adhesive strength (Lap) between graphite and polyurethane binder according to the degree of crosslinking of the polyurethane binder.

FIG. 4 is a graph showing shear adhesive strength (Lap) between copper and a polyurethane binder according to the degree of crosslinking of the polyurethane binder.

5 is a discharge capacity graph according to the number of charge and discharge cycles.

6 to 17 are scanning electron microscope (SEM) photographs showing the change in thickness of the electrode according to charge and discharge.

The present invention relates to an electrode, a method for manufacturing the same, a polymer electrolyte composition and a lithium battery employing the same, and more particularly, an electrode including a polyurethane binder having excellent binding force, elasticity, and charge / discharge characteristics and capable of adjusting elongation rate, The manufacturing method, the polymer electrolyte composition, and the lithium battery which employ | adopted these are related.

Lithium batteries have been widely used as a power source for portable electronic devices because they have high voltage, good energy density, and improved safety compared to nickel card batteries. However, increasingly, high capacity, miniaturization, and light weight of portable electronic devices are required, and thus, improved battery characteristics such as higher driving voltage, increased lifespan, and higher energy density than conventional lithium batteries are required. Efforts have been made to improve the performance of various components of lithium batteries to meet these demands. The characteristics of the battery largely depend on the electrode, the electrolyte, and other battery materials used. In the case of the electrode, the characteristics are determined by the electrode active material, the current collector, and a binder for imparting adhesion therebetween. Since the content and type of the active material used determine the amount of lithium ions that can be combined with the active material, a battery having a higher capacity can be obtained as the amount of the active material is increased and the active material having a large intrinsic capacity is used. In addition, when the binder shows excellent adhesion between the active materials or between the active material and the current collector, the electrons and lithium ions are smoothly moved in the electrode and the internal resistance of the electrode is reduced to allow relatively high rate charge and discharge. . In the case of a high capacity battery, a composite electrode using a mixture of metal and graphite is required, so that the volume of the active material is greatly expanded and contracted during charging and discharging, so that the binder has excellent elasticity and recovery ability in addition to excellent adhesive force. It should be possible to maintain the original adhesion and electrode structure despite repeated expansion and contraction of significant electrode volume.

Polyvinylidene fluoride (PVDF) -based polymer, a conventional binder material, is used in admixture with a solvent such as N-methyl-2-pyrrolidone. Although it has good adhesive strength, its elongation rate is about 10%, and its elasticity is insufficient. In order to maintain, the input amount must be large and it is difficult to manufacture because it is mixed with an organic solvent. Another representative binder material, styrene-butadiene rubber (SBR), of course, is excellent in elasticity, but has weakness in adhesion and weakness, so that the structure of the electrode cannot be maintained as charging and discharging are repeated. Therefore, generally, the two binder materials are mixed and used, or merely a simple mixture thereof, which is a situation in which performance improvement is limited.

Various kinds of binders have recently been proposed to solve the problems of the prior art.

Korean Patent Publication No. 2001-0025099 discloses a binder resin having high ion conductivity and adhesion by introducing a substituent having a large dipole moment into polyurethane. However, since the binder resin is not dissolved in water, there is a disadvantage in that an organic solvent must be used, and there is a problem in that mechanical properties such as elasticity are inferior because a chain extender is not used separately.

Korean Laid-Open Patent Publication No. 2004-0104400 discloses a composite binder polymer for electrodes in which a dispersant is chemically bonded. The polymer is an olefinic monomer and is a polymer that can be water-dispersed using a polyalkylene oxide, an acrylic acid derivative, and a reactive surfactant as a dispersant. The binder polymer is excellent in dispersing properties but has a problem of relatively inferior elasticity.

Korean Laid-Open Patent Publication No. 2004-0078927 discloses a binder including composite polymer particles having two or more phase structures having different physical properties. The composite polymer has a structure in which a single phase, a polymer region having excellent conductivity, and a two phase, a polymer region having excellent adhesion, are bonded in a core / shell structure. Such a composite structure shows improved physical properties than simply mixing polymers of different physical properties, but there is a problem that an organic solvent should be used without considering dispersion properties.

Therefore, there is still a need to provide a binder that can overcome the problems of the prior art and can produce a battery having excellent elasticity and adhesive strength as a result of water dispersion and improved charge and discharge characteristics.

The first technical problem to be achieved by the present invention is to provide an electrode employing a binder excellent in elasticity and adhesion.

The second technical problem to be achieved by the present invention is to provide a method for manufacturing the electrode.

The third technical problem to be achieved by the present invention is to provide a polymer electrolyte composition excellent in solubility and adhesion to the electrolyte.

The fourth technical problem to be achieved by the present invention is to provide a lithium battery employing the electrode.

The present invention to achieve the first technical problem,

Provided is a binder for an energy storage device comprising a dispersed polyurethane polymer compound.

According to one embodiment of the present invention, the water-dispersed polyurethane polymer compound is preferably obtained by reacting a polyurethane compound obtained by reacting a polyol compound, a diisocyanate compound and a dispersant with a neutralizing agent and a chain extender.

According to one embodiment of the present invention, the dispersant may be any compound having two hydroxyl groups in the molecular structure and at least one group capable of dissociating into a cation or an anion, dimethylol butanoic acid, dimethylol propionic acid, methylene diethanolamine , And nonionic polyethylene oxide derivatives are preferable.

According to one embodiment of the present invention, the dispersant is preferably 2 to 7% by weight of the total solid of the polyurethane polymer compound.

According to one embodiment of the present invention, the neutralizing agent is preferably triethylamine, sodium hydroxide, potassium hydroxide, lithium hydroxide and the like.

According to one embodiment of the present invention, the chain extender is a diamine having a relatively small molecular weight of 2 to 6 carbon atoms, ethylenediamine, propanediamine, butylenediamine, hexanediamine, isophoronediamine, xylene diamine, diethyl toluene Diamine, diethylene triamine, triethylene tetraamine, etc. are preferable.

Alternatively, the present invention to achieve the first technical problem,

Provided is a binder for an energy storage device comprising a crosslinked polyurethane polymer compound obtained by reacting a water-dispersed polyurethane polymer compound with a crosslinking agent.

According to one embodiment of the present invention, the crosslinking agent is preferably aziridine, oxazoline, modified diisocyanate and diepoxide compound.

The present invention to achieve the second technical problem,

A binder comprising a dispersed polyurethane polymer compound; And

Electrode active material;

It provides an electrode that is prepared to include.

Alternatively, the present invention to achieve the second technical problem,

A binder comprising a crosslinked polyurethane polymer compound obtained by reacting a water-dispersed polyurethane polymer compound with a crosslinking agent; And

Electrode active material;

It provides an electrode that is prepared to include.

The present invention to achieve the third technical problem,

Preparing a slurry for electrodes by simultaneously mixing the dispersed polyurethane polymer compound, the electrode active material and the crosslinking agent;

Applying the slurry to a current collector before the crosslinking reaction is completed;

It provides an electrode manufacturing method comprising a.

The present invention to achieve the fourth technical problem,

Ion conductive salts;

Polar solvents; And

Crosslinked polyurethane polymer compounds;

It provides a polymer electrolyte composition comprising a.

The present invention to achieve the fifth technical problem,

Provided is a lithium battery employing the above electrode.

Alternatively, the present invention to achieve the fifth technical problem,

It provides a lithium battery employing a polymer electrolyte layer containing the polymer electrolyte composition.

In another aspect, the present invention to achieve the fifth technical problem,

The electrode; And

A polymer electrolyte layer comprising the polymer electrolyte composition according to the above interposed between the electrodes;

It provides a lithium battery prepared to include.

Hereinafter, the present invention will be described in more detail.

The electrode according to the present invention improves the adhesive force by using a polyurethane polymer compound dispersed in water and also improves elasticity by curing the polymer compound having excellent dispersing properties by a crosslinking reaction to improve elasticity and charge / discharge. It is possible to have characteristics.

The present invention provides a binder for an energy storage device comprising a dispersed polyurethane polymer compound. Since the binder containing the dispersed polyurethane polymer compound provides adhesion in addition to elasticity and is dispersed in water, it is economically inexpensive, environmentally friendly, and easy to handle because it avoids the use of organic solvents in electrode production. Has

In the binder, the water-dispersed polyurethane polymer compound may be prepared by reacting a polyurethane compound obtained by reacting a polyol compound, a diisocyanate compound, and a dispersing agent with a neutralizing agent and a chain extender.

In more detail with respect to the compounds for producing the dispersed polyurethane polymer compound, the diisocyanate compound may be any of alicyclic isocyanate, aliphatic isocyanate and aromatic isocyanate having two or more isocyanate groups in the molecule. For example, methylene diphenyl diisocyanate (MDI), polymeric methylene diphenyl diisocyanate (polymeric MDI), tolylene diisocyanate (TDI), lysine diisocyanate (LDI), hydrogenated tolylene diisocyanate, hexamethylene diisocyanate ( HDI), xylene diisocyanate (XDI), hydrogenated xylene diisocyanate, naphthylene diisocyanate (NDI), biphenylene diisocyanate, 2,4,6-triisopropylphenyl diisocyanate (TIDI), diphenyl Ether diisocyanate, tolidine diisocyanate (TODI), isophorone diisocyanate (IPDI), 4,4'-dicyclohexyl methane diisocyanate (HMDI), tetramethylxylene diisocyanate (TMXDI), 2,2,4- Trimethylhexamethylene diisocyanate (TMHDI), 1,12-diisocyanatododecane (DDI), norbornane diisocyanate (NBDI), 2,4-bis- (8-isocyanatooctyl) -1,3-di Octyl Chlorobutane (OCDI), 2,2,4 (2,4,4) -trimethylhexamethylene diisocyanate (TMDI), naphthalene-crosslinked polyphenyl polyisocyanate, and the like. It can be mixed and used.

Examples of the polyol compound include polymers such as polyether polyols such as polyethylene glycol, polypropylene glycol, ethylene glycol propylene glycol copolymers and polytetramethylene ether glycol, or polyester polyols, polycaprolactone diols, and polybutadiene diols. Polyol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-dimethyl -1,3-propanediol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanedimethanol, 1,4-bis-(??-hydroxy) benzene, p-xylylenediol, phenyldiethanol Amines, methyldiethanolamine, 3,9-bis (2-hydroxy-1,1-dimethyl) -2,4,8,10-tetraoxaspiro [5,5] -undecane, and the like. It is not limited, The use of the polyol which has three or more alcohol groups is also possible.

In the case of a polyol, the weight average molecular weight (M _W ) is preferably 200 to 10,000, more preferably 500 to 8000, most preferably 1000 to 6000. If the weight average molecular weight of the polyol is less than 200, there is a problem that the physical properties of the polyurethane compound obtained by the reaction is lowered, while if the weight average molecular weight exceeds 10000, the viscosity is excessively increased, which makes handling difficult.

Moreover, monohydric alcohol can also be used for reaction as needed. Methanol, ethanol, butanol, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, etc. are mentioned as monohydric alcohol. Also, polyethylene glycol monoethyl ether, polypropylene glycol monoethyl ether, and ethylene glycol propylene glycol copolymer monoethyl ether, in which one end of polyethylene glycol, polypropylene glycol, ethylene glycol propylene glycol copolymer, etc. is substituted with a methyl group or an ethyl group Etc. can also be used.

In the present invention, the dispersant used to impart the water dispersion properties may be any compound having two hydroxyl groups in the molecular structure and at least one group capable of dissociating into a cation or an anion, dimethylol butanoic acid (DMBA), dimethyl All propionic acid (DMPA), methylene diethanolamine, and nonionic polyethylene oxide derivatives are preferable. The dispersant is preferably 2 to 7% by weight of the total solid of the polyurethane polymer compound. If it is less than 2% by weight, there is a problem that the dispersion stability of the polymer is lowered, and if it is more than 7% by weight, the polarity due to the excessive amount of the dispersant is increased, thereby weakening the chemical resistance and water resistance.

Such carboxyl diols can be neutralized as base compounds or cationic metals, and have a water dispersion characteristic only since they are neutralized chemically to form salts. Base compounds that may be used herein include, but are not limited to, triethylamine (TEA), sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH), and the like. Each base compound may be appropriately selected and used depending on the application and application field, or the type of diol used, and since the big difference is difficult to explain the characteristics thereof, it is omitted herein.

The amines used in the present invention include diamines having a relatively small molecular weight of 2 to 6 carbon atoms, ethylenediamine (EDA), propanediamine (PDA), butylenediamine (BDA), hexanediamine (HDA), and isophoronediamine (IPDA). ) Divalent amines such as xylene diamine (XDA), diethyl toluene diamine (DETDA), diethylene triamine (DETA), triethylene tetraamine (TETA) and the like are preferred, but not limited thereto.

Alternatively, the present invention provides a binder for an energy storage device comprising a crosslinked polyurethane polymer compound obtained by reacting the water-dispersed polyurethane polymer compound with a crosslinking agent.

In the binder, the crosslinking agent is preferably at least one compound selected from the group consisting of aziridine, oxazoline, modified diisocyanate and diepoxide compound. Specifically, the crosslinking agent is preferably a compound that can be combined with a reactor that enables water dispersion of the polyurethane polymer, such as aziridine, oxazoline, modified diisocyanate and diepoxide compound. The crosslinker is not necessarily a single molecule and may be in the form of oligomers in which two or more molecules are connected.

The present invention provides an electrode comprising a binder and an electrode active material comprising a dispersed polyurethane polymer compound. The binder comprising the dispersed polyurethane polymer compound is the same as described above. The electrode active material is not particularly limited as long as it is used in the art.

Alternatively, the electrode according to the present invention provides an electrode including a binder and an electrode active material including a crosslinked polyurethane polymer compound obtained by reacting the dispersed polyurethane polymer compound with the crosslinking agent.

The binder containing the crosslinked polyurethane polymer compound is water-dispersible by the reaction with the crosslinking agent and the solubility characteristics of the electrolyte solution using the organic solvent is improved to improve the compatibility. By such a crosslinking reaction, the elasticity of the polymer is further improved to increase the restoring force. Therefore, the electrode employing the binder can maintain most of the initial volume and adhesive force despite the significant volume change occurring during charging and discharging of the electrode, thereby enabling improved battery performance and lifespan.

Specifically, a method of manufacturing an electrode including the binder and the electrode active material may be specifically described. In the case of the negative electrode, the negative electrode active material and the negative electrode mixture material including the binder may be molded into a predetermined shape, and the negative electrode mixture material may be formed of copper foil or the like. It is also preferable to manufacture by the method of apply | coating to the electrical power collector of.

More specifically, a negative electrode material composition is prepared and directly coated on a copper foil current collector, or cast on a separate support and a negative electrode active material film peeled from the support is laminated on the copper foil current collector to obtain a negative electrode plate. In addition, the negative electrode of this invention is not limited to the form enumerated above, The form other than the enumerated form is possible.

In order to increase the capacity of the battery, it is necessary to charge and discharge a large amount of current, and for this purpose, a material having low electrical resistance of the electrode is required. Therefore, in order to reduce the resistance of the electrode, the addition of various conductive agents is common, and mainly used conductive agents include carbon black and graphite fine particles. However, since the negative electrode of the present invention has excellent conductivity in itself, it is not necessary to add a separate conductive agent.

In the case of a positive electrode, a positive electrode active material composition is prepared by mixing a positive electrode active material, a conductive agent, the binder, and a solvent. The positive electrode active material composition is directly coated on a metal current collector and dried to prepare a positive electrode plate. It is also possible to produce the positive electrode plate by casting the positive electrode active material composition on a separate support, and then laminating the film obtained by peeling from the support onto a metal current collector.

The positive electrode active material may be any lithium-containing metal oxide, as long as it is commonly used in the art, for example, LiCoO ₂ , LiMn _x O _2x , LiNi _1-x Mn _x O _2x (x = 1, 2), Ni _1-xy Co _x Mn _y O ₂ (0 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.5) and the like, and more specifically, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , LiFeO ₂ , V ₂ O ₅ And compounds capable of redoxing lithium such as TiS and MoS.

Carbon black is used as the conductive agent, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polytetrafluoroethylene and mixtures thereof, Styrene butadiene rubber-based polymer is used, and N-methylpyrrolidone, acetone, water and the like are used as the solvent. At this time, the content of the positive electrode active material, the conductive agent, the binder, and the solvent is at a level commonly used in lithium batteries.

Meanwhile, the present invention provides a polymer electrolyte composition comprising an ion conductive salt, a polar solvent, and a crosslinked polyurethane polymer compound. The polymer electrolyte composition has the ability to dissolve the ion conductive salt in a high concentration, and even after such dissolution, it is difficult to recombine ions, and thus the ion conductivity is not lowered. Thus, the polymer electrolyte composition is a crosslinked polyurethane polymer compound and an ion conductive salt. It has as a main component. In this case, the ion conductive salt may be used without particular limitation as long as it is usually used in an energy storage device. Specific examples thereof will be listed in the description of a battery employing the polymer electrolyte composition.

Specifically, the amount of the ion conductive salt blended in the polymer electrolyte composition may be used in various ways depending on the conditions, but usually 5 to 1000 parts by weight based on 100 parts by weight of the dry polymer compound, preferably 10 to 500 parts by weight More preferably, it is 10-100 weight part, Most preferably, it is 10-50 weight part. When the amount of the ion conductive salt is less than 5 parts by weight, the total ion concentration is low, resulting in excessively low conductivity, and when it exceeds 1000 parts by weight, there is a problem that precipitation of salts occurs.

On the other hand, the organic solvent used in the polymer electrolyte will be mentioned in more detail below. The amount of the solvent added is preferably 1 to 90% by weight, more preferably 25 to 75% by weight based on the total weight of the polymer electrolyte composition. When there is too much addition amount of a solvent, the adhesiveness which the polymer for polymer electrolytes has may be impaired. The ion conductive polymer electrolyte has high ion conductivity and high adhesiveness, and is disposed between the positive electrode and the negative electrode in addition to serving as a polymer electrolyte, and serves to firmly adhere the positive electrode and the negative electrode, and various secondary batteries such as film batteries. It is suitable as a solid electrolyte of.

The method for thinning the ion conductive solid polymer electrolyte in the manufacturing process is not particularly limited. For example, the film solid may be coated in a uniform thickness by means of roller coating, screen coating, doctor blade method, spin coating, bar coater, or the like. An electrolyte layer can be obtained.

The lithium battery of the present invention may be prepared by employing the electrode described above as a positive electrode or a negative electrode or both, alternatively may be prepared using a polymer electrolyte layer comprising the polymer electrolyte composition described above as a separate composition, The positive electrode and the negative electrode may be used as it is conventionally used electrodes.

Alternatively, the positive electrode and the negative electrode employing the electrode according to the present invention and the polymer electrolyte layer including the polymer electrolyte composition according to the present invention interposed between the positive electrode and the negative electrode may be prepared simultaneously.

 As the separator, any one commonly used in lithium batteries can be used, and the polymer electrolyte composition is also included. In particular, it is preferable that it is low resistance with respect to the ion migration of electrolyte, and is excellent in electrolyte-moisture capability. More specifically, the material selected from glass fiber, polyester, teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), and combinations thereof may be nonwoven or woven. In more detail, in the case of a lithium ion battery, a wound separator made of a material such as polyethylene or polypropylene is used. In the case of a lithium ion polymer battery, a separator having excellent organic electrolyte impregnation ability is used. It can be manufactured according to the method.

That is, a separator composition is prepared by mixing a polymer resin, a filler, and a solvent, and the separator composition is directly coated and dried on an electrode to form a separator film, or the separator composition is cast and dried on a support, and then the support The separator film peeled off can be laminated on the electrode and formed.

The polymer resin is not particularly limited, and any material used for the binder of the electrode plate may be used. For example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate and mixtures thereof can be used.

Examples of the electrolyte include propylene carbonate, ethylene carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, butylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, and dioxo Column, 4-methyldioxolane, N, N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, dimethyl carbonate LiPF ₆ , LiBF ₄ in a solvent such as methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, dipropyl carbonate, dibutyl carbonate, diethylene glycol or dimethyl ether, or a mixed solvent thereof. , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO2) (C _y F _{2y + 1} SO ₂ ) (where x and y are natural waters), one or more electrolytes consisting of lithium salts such as LiCl and LiI or a mixture of two or more thereof are dissolved Can be used.

As described above, the separator is disposed between the positive electrode plate and the negative electrode plate to form a battery structure. The battery structure is wound or folded, placed in a cylindrical battery case or a square battery case, and then the organic electrolyte solution of the present invention is injected to complete a lithium ion battery.

In addition, after stacking the battery structure in a bi-cell structure, it is impregnated in an organic electrolyte, and the resultant is placed in a pouch and sealed to complete a lithium ion polymer battery.

In the method for preparing an electrode according to the present invention, a slurry for the electrode is prepared by simultaneously mixing a dispersed polyurethane polymer compound, an electrode active material, and a crosslinking agent, and then a crosslinking reaction is completed between the dispersed polyurethane polymer compound and the crosslinking agent. The slurry is applied to a current collector before the preparation, to provide a method for producing an electrode. In this case, since the crosslinking reaction proceeds in a state of being mixed with the electrode active material, the binder may be evenly formed throughout the electrode, thereby obtaining uniform physical properties. In the above method, the crosslinking agent may be prepared by mixing at the same time, but it is also possible to first mix the other slurry components and then mix the slurry just before applying to the current collector.

The method of preparing the crosslinked polyethylene polymer compound according to the present invention will be described in detail. First, an excess of a diisocyanate compound and a polyol compound is reacted to prepare a prepolymer. In this case, the amount of diisocyanate to polyol is preferably 1.01: 1 to 4: 1 in an equivalent ratio, more preferably 1.1: 1 to 3: 1 and most preferably 2: 1. When the ratio of the diisocyanate compound is more than 4 or less than 1.01, there is a problem in that the polymer having a large molecular weight cannot be formed.

 Here, the prepolymer and the dispersant are reacted to prepare a polyurethane compound. Next, the polyurethane compound is contacted with a neutralizing agent to form a dispersant in the form of a salt, and then dispersed in water to prepare a dispersed polyurethane compound. In this case, the water-dispersed polyurethane compound preferably has a solid content of 15 to 60% by weight. Here, the water-dispersed polyurethane compound and the chain extender are reacted to obtain a water-dispersed polyurethane polymer compound. The chain extender gives the polyurethane compound mechanical properties. The amount of the chain extender should be 1: 1 so that the residual unreacted cyan group and the equivalent ratio of the water-dispersed polyurethane compound produced in the above process, and if the content exceeds or is less than the molecular weight of the polyurethane does not increase sufficiently. Therefore, there is a problem that the physical properties inherent in polyurethane cannot be exhibited. Such manufacturing reactions and processes are generally known in the art, and in the case of the present invention, it is preferably carried out for about 1 to 8 hours under a nitrogen atmosphere which is not in contact with air and a temperature condition of about 40 to 90 ° C, More preferably, it is carried out at about 60 to 80 ℃ for about 5 to 6 hours.

On the other hand, in order to produce a cross-linked polyurethane high molecular compound, a crosslinking agent is further reacted with the water-dispersed polyurethane high molecular compound to obtain a cross-linked polyurethane high molecular compound. Due to this crosslinking reaction, the polyurethane polymer compound loses water dispersibility.

The present invention will be described in more detail with reference to the following Preparation Examples, Examples and Comparative Examples. However, an Example is for illustrating this invention and does not limit the scope of the present invention only by these.

Preparation of Polyurethane Polymer Compound

Preparation Example 1

99.59 g of IPDI and 11.19 g of DMBA were placed in a 1 L round bottom sand dune reactor and stirred slowly in a nitrogen atmosphere. 150 g of PTMEG was added two or three times while maintaining the temperature at about 40 ° C. When the temperature was stabilized after the addition, the reaction was continued for 4 to 6 hours while maintaining the temperature at 60 ° C. until both ends of the polyol reached the theoretical NCO value corresponding to the IPDI connection. When the theoretical NCO% was reached, the solution was cooled to 30 ° C, and 7.53 g of TEA having the same mole number as DMBA was added thereto. The reaction was neutralized for about 30 to 40 minutes while maintaining the temperature of 40 ℃. After the neutralization reaction, after cooling to 20 ° C. or lower, 381.54 g except for 30 g was added to 411.54 g of distilled water required for 40 wt% of solids, and the mixture was stirred and stirred at a speed of rpm = 1000. When the dispersion stabilized, 13.44 g of EDA required for chain extension was dissolved in 30 g of distilled water, and then slowly added to the reactor. When EDA entered, a rapid exotherm occurred and the reactor temperature rose to 40 ° C. or higher. After stabilizing the furnace temperature and reacting for about 3 hours, a dispersion polyurethane was obtained.

Preparation Example 2

It was prepared under the same conditions as Preparation Example 1, except that 9.53 g was used instead of 11.19 g of dimethylolbutanoic acid.

Preparation Example 3

It was prepared under the same conditions as Preparation Example 1, except that 150 g of polypropylene glycol was used instead of 150 g of polytetramethylene ether glycol.

Preparation Example 4

It was prepared under the same conditions as Preparation Example 2 except that 150 g of polypropylene glycol was used instead of 150 g of polytetramethylene ether glycol.

Preparation Example 5

Preparation was carried out under the same conditions as Preparation Example 3, except that 11.36 g of dimethylolpropionic acid was used instead of 11.19 g of dimethylolbutanonic acid.

Preparation Example 6

It was prepared under the same conditions as Preparation Example 5, except that 150 g of polycaprolactone diol was used instead of 150 g of polypropylene glycol.

Preparation Example 7

The crosslinked reaction was carried out to the water-dispersed polyurethane polymer compound obtained in Preparation Example 1 by adding aziridine (Trimethylolpropane Tris (2-Methyl-1-Aziridinepropionate) corresponding to 30 mol% of the carboxyl groups present in the polymer compound. Polyurethane polymer compounds were prepared.

Preparation Example 8

The crosslinked reaction was carried out to the water-dispersed polyurethane polymer compound obtained in Preparation Example 1 by adding aziridine (Trimethylolpropane Tris (2-Methyl-1-Aziridinepropionate) corresponding to 70 mol% of the carboxyl groups present in the polymer compound. Polyurethane polymer compounds were prepared.

Preparation Example 9

The crosslinked reaction was performed by adding crosslinking reaction of a water-dispersed polyurethane polymer compound obtained in Preparation Example 1 to 100 mol% of trimethylolpropane Tris (2-Methyl-1-Aziridinepropionate). Polyurethane polymer compounds were prepared.

Preparation Example 10

A crosslinking reaction was carried out by adding an oxazoline (POCROSS WS-series Oxazoline Reactive Polymer / Water, Nippon Shokubai Co., Ltd.) corresponding to 30 mol% of the carboxyl groups present in the polymer compound to the water-dispersed polyurethane polymer compound obtained in Preparation Example 1. To prepare a crosslinked polyurethane polymer compound.

Preparation Example 11

A crosslinking reaction was carried out to the water-dispersed polyurethane polymer compound obtained in Preparation Example 1 by adding oxazoline (POCROSS WS-series Oxazoline Reactive polymer / Water, Nippon Shokubai) corresponding to 70 mol% of the carboxyl groups present in the polymer compound. A crosslinked polyurethane polymer compound was prepared.

Preparation Examples 12-16

Preparation was carried out under the same conditions as in Production Examples 7 to 11, except that the water dispersion polyurethane polymer compound obtained in Preparation Example 6 was used instead of the water dispersion polyurethane polymer compound obtained in Preparation Example 1.

Preparation Examples 17-22

To each water-dispersed polyurethane polymer compound obtained in Production Examples 1 to 6, cross-linked with oxazoline (POCROSS WS-series Oxazoline Reactive polymer / Water from Nippon Shokubai), which corresponds to 30 mol% of the carboxyl groups present in the polymer compound, was added. Prepared by carrying out the reaction.

Preparation Examples 23 to 28

Crosslinking with the addition of oxazoline (POCROSS WS-series Oxazoline Reactive polymer / Water from Nippon Shokubai) corresponding to 70 mol% of the carboxyl groups present in the polymer compound to each of the water-dispersed polyurethane polymer compounds obtained in Production Examples 1 to 6 Prepared by carrying out the reaction.

Comparative Example 1

Commercially available styrene-butadiene rubber (SBR) (BZ400B, ZEON, Japan) was used as it is.

Comparative Example 2

Commercially available polyvinylidene fluoride (PVDF) (Kureha, KF1100) was used as it is.

Stress-strain experiment

Stress deformation experiments were performed using the polyurethane films prepared in Preparation Examples 1 and 7 to 11 and the polyurethane films prepared in Preparation Examples 6 and 12 to 16. It was measured using a universal testing machine (METOY) AMETEK of LLOYD, the tensile speed was 500 mm / min, the experimental results are shown in Figures 1 and 2.

As shown in FIG. 1 and FIG. 2, the stress increases and the elongation rate decreases as the degree of crosslinking increases due to the change in crosslinking agent content.

Adhesion Test

Adhesive force was measured using the polyurethane films, styrene-butadiene films and polyvinylidene fluoride films prepared in Preparation Examples 1 to 6, Preparation Examples 17 to 22, Preparation Examples 23 to 28, and Comparative Examples 1 and 2. Experiment was conducted according to the lap shear adhesive strength test method of ASTM 1002, Figure 3 is a graph showing the adhesion strength with graphite according to the crosslinking degree and Figure 4 is the adhesion strength with copper (Lap: shear adhesive strength, shear adhesive strength) is a graph showing the degree of crosslinking.

As shown in FIGS. 3 and 4, as the degree of crosslinking increases, the adhesion tends to decrease, but shows improved adhesion as compared to styrene-butadiene rubber and polyvinylidene fluoride, which are comparative examples, and as the degree of crosslinking increases, the elasticity increases. This results in improved resilience. Therefore, it is possible to determine the preferred degree of crosslinking in consideration of both adhesive force and elasticity.

Cathode manufacturing

Example 1

1.5 g each of the water-dispersed polyurethane and carboxy methyl cellulose (CMC) prepared in Preparation Example 1 were mixed at a weight ratio of 1: 1, and an oxazoline (Nippon) corresponding to 50 mol% of the carboxyl groups present in the polymer compounds. Shokubai POCROSS WS-series Oxazoline Reactive polymer (Water) 0.62g to prepare a binder added as a crosslinking agent.

200 g of distilled water, 20 g of a conductive agent (Timcal's graphite-based conductive agent, trade name SFG6), and 77 g of a negative electrode active material (a composite active material consisting of graphite, silicon metal, and carbon of Osaka Gas Chemical) were mixed with 3 g of a binder, and then using a mechanical stirrer. The slurry was prepared by stirring for 60 minutes.

This slurry was applied to a copper (Cu) current collector using a doctor blade to a thickness of about 60 ~ 70㎛, dried and once again under vacuum, 120 ℃ Celsius to prepare a negative electrode plate.

Example 2

The same conditions as in Example 1 except that 100 mol% of trimethylolpropane Tris (2-Methyl-1-Aziridinepropionate) was used instead of 50 mol% of oxazoline (POCROSS WS-series Oxazoline Reactive polymer / Water from Nippon Shokubai) A negative electrode plate was prepared.

Comparative Example 3

A negative electrode plate was prepared under the same conditions as in Example 1 except that styrene-butadiene rubber (SBR) was used instead of the water-dispersed polyurethane.

Lithium battery manufacturers

The negative electrode plates prepared in Examples 1, 2 and Comparative Example 3 were made of lithium metal as a counter electrode, and a PTFE separator and 1M LiPF ₆ were EC (ethylene carbonate) + DEC (diethyl carbonate) (3: 7). ) Was prepared as a coin cell of the 2015 standard using the solution dissolved in the electrolyte.

Charge / discharge experiment

The manufactured coin cell was charged with a constant current until reaching 0.001 V with respect to the Li electrode at a current of 150 mA per gram of the active material, followed by a constant voltage until the current was lowered to 7.5 mA per gram of the active material while maintaining a voltage of 0.001 V. Filling was performed.

 After the charging was completed, the cell passed about 30 minutes of rest and then discharged at a constant current until 150 V was reached at a current of 150 mA per 1 g of the active material.

Experimental results of the Preparation Example and Comparative Example are shown in FIG. Each experiment was performed twice under the same conditions. As shown in FIG. 5, in the case of Comparative Example 3, the discharge capacity decreases at about 18 cycles, and the inclination is also large, whereas in Examples 1 and 2, the discharge cycles exceed 20 cycles. There is a decrease in capacity and the slope is relatively gentle. In the case of polyurethane binder, it has improved elasticity or restoring force compared to conventional styrene-butadiene rubber binder and improves adhesive strength, thereby maintaining adhesion to the active material and the current collector in spite of the volume change of the negative electrode active material generated during charging and discharging. The reason is that cracks do not occur inside the electrode, and thus reversible movement of ions is possible.

Measurement of volume change of the electrode

The thickness of the electrode changed after the charge / discharge experiment of the battery was measured to evaluate the degree of volume retention of the electrode that changes as charge and discharge progress. Immediately after electrode preparation, the thickness of the electrode cross section at two charge and discharge cycles and after 50 charge and discharge cycles was measured using a scanning electron microscope. The results are shown in Table 1 and FIGS. 6 to 17.

Electrode status Average thickness (㎛) Thickness change rate (%) Immediately after manufacture 69.1 - 2nd lithium occlusion state 97.2 40.67 2nd Lithium Release Status 77.4 11.94 50th Lithium Release Status 88.3 27.79 Immediately after manufacture 61.9 - 2nd lithium occlusion state 84.9 37.16 2nd Lithium Release Status 65.5 5.82 50th Lithium Release Status 71.8 15.99 Immediately after manufacture 70.9 - 2nd lithium occlusion state 95.6 34.93 2nd Lithium Release Status 71.4 0.78 50th Lithium Release Status 72.6 2.47

As shown in Table 1, in Examples 1 and 2, the change in thickness of the electrode after 50 charge / discharge cycles was less than 16%, but in Comparative Example 3, the resilience was relatively excellent in the case of manufacturing example, exceeding 27%. Showed. This improved restoring force is believed to be due to the improved elasticity of the crosslinked polyurethane binder. In addition, in the case of Example 2 having a crosslinking degree of 100 mol%, the thickness change of the electrode after 50 charge / discharge cycles was less than 3%, which clearly shows that the crosslinking degree has improved elasticity. This can be more clearly confirmed with the electron micrographs (SEM) of FIGS. 6 to 17. As shown in FIG. 9, in the case of Comparative Example 3, after 50 charge / discharge cycles, the electrode form was swollen from the plane, resulting in a decrease in electrode density resulting in an increase in porosity and consequently a decrease in conductivity. It can be expected that the life characteristics of the battery will decrease, thereby increasing.

The electrode according to the present invention improves the adhesive force by using a polyurethane polymer compound dispersed in water and also by adjusting the elasticity and adhesive force while improving the elasticity by curing the polymer compound having excellent dispersion characteristics by a crosslinking reaction, it is adopted. It is possible that one battery has improved restoring force and charge / discharge characteristics.

Claims (15)

Binder for Energy Storage Devices Containing Dispersed Polyurethane Polymer Compound The binder according to claim 1, wherein the dispersed polyurethane polymer compound is obtained by reacting a polyurethane compound obtained by reacting a polyol compound, a diisocyanate compound, and a dispersing agent with a neutralizing agent and a chain extender. The compound of claim 2, wherein the dispersant is a compound having two hydroxyl groups in a molecular structure and at least one group that can be dissociated into a cation or an anion. A binder, characterized in that at least one compound selected from the group consisting of derivatives. The binder according to claim 2, wherein the dispersant is 2 to 7 wt% of the total solid of the polyurethane polymer compound. 3. The binder according to claim 2, wherein the neutralizing agent is at least one compound selected from the group consisting of triethylamine, sodium hydroxide, potassium hydroxide, and lithium hydroxide. 3. The method of claim 2, wherein the chain extender is selected from the group consisting of ethylenediamine, butylenediamine, propanediamine, hexanediamine, isophoronediamine, xylene diamine, diethyl toluene diamine, diethylene triamine, and triethylene tetraamine. A binder, characterized in that at least one compound selected. A binder for an energy storage device comprising a crosslinked polyurethane polymer compound obtained by reacting a water-dispersed polyurethane polymer compound with a crosslinking agent 8. The binder according to claim 7, wherein the crosslinking agent is at least one compound selected from the group consisting of aziridine, oxazoline and modified diisocyanate and diepoxide compound. A binder comprising a dispersed polyurethane polymer compound; And Electrode active material; Electrode characterized in that it comprises a. A binder comprising a crosslinked polyurethane polymer compound obtained by reacting a water-dispersed polyurethane polymer compound with a crosslinking agent; And Electrode active material; Electrode characterized in that it is prepared to include. Preparing a slurry for electrodes by simultaneously mixing the dispersed polyurethane polymer compound, the electrode active material and the crosslinking agent; Applying the slurry to a current collector before the crosslinking reaction is completed; Electrode manufacturing method comprising a. Ion conductive salts; Polar solvents; And Crosslinked polyurethane polymer compounds; Polymer electrolyte composition comprising a. The lithium battery which employ | adopted the electrode of Claim 9 or 10. A lithium battery comprising a polymer electrolyte layer comprising the polymer electrolyte composition according to claim 12. An electrode according to claim 9; And A polymer electrolyte layer comprising the polymer electrolyte composition according to claim 12 interposed between the electrodes; Lithium battery characterized in that it is prepared, including.

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